Reptile UVB Calculator
Get exact UVB bulb type, distance and hours for 10 reptile species — based on Ferguson Zone data
🦎 Reptile UVB Calculator
Get the exact UVB bulb, distance, and hours for your reptile species
Why UVB Lighting Is Critical for Reptiles
UVB radiation is essential for reptiles to synthesise Vitamin D3 in their skin. Without adequate D3, reptiles cannot absorb calcium — leading to Metabolic Bone Disease (MBD), a painful and often fatal condition that causes soft bones, deformities, and seizures.
The Ferguson Zone System
The Ferguson Zone system classifies reptile species by their natural UVB exposure in the wild. Zone 1 species (crepuscular, shade-dwelling) need low UVB. Zone 4 species (basking in open desert sun) need intense UVB. Matching your lighting to your species’ natural zone is the foundation of modern reptile husbandry.
T5 vs T8 Bulbs — What’s the Difference?
T5 HO (High Output) bulbs produce significantly more UVB than T8 bulbs of the same percentage rating. For most species, T5 HO is the recommended standard. T8 bulbs can work for low-UVB species kept in small enclosures but are generally being phased out by experienced keepers.
The Most Important Thing Most Keepers Miss
UVB bulbs degrade invisibly. The bulb may still produce visible light long after UVB output has dropped to useless levels. Replace your UVB bulb every 6 months regardless of whether it still looks bright. A UV Index meter (UVI meter) is the only way to verify actual output.
Glass Blocks UVB Almost Completely
Standard glass blocks up to 95% of UVB. If your enclosure has a glass top, the UVB bulb must be placed inside the enclosure — not on top of the glass.